Burndown chart show as a red horizontal line

Hi i am using scrum board in jira , i have customized column set . To Do Development In Progress Ready For Code Review Code Review In Progress Ready For Testing Testing In Progress Approved For Release Released Approved ,

instead of new , in progress , to do .

in my burn-down chart even after i added spent time or make the task approved , the burn down chart is shown as a strait red horizontal line , why is that ?